The present invention relates broadly to equipment self-repair devices and in particular to an equipment self-repair apparatus utilizing adaptive multifunction modules to replace faulty logic modules.
In the prior art, circuit reliability is increased through the use of redundant circuits. These redundant circuits are introduced, in the event of a failure, through the use of logic circuits such as an OR or a NOR gate. One of the prior art repair methods involves the use of redundant binary logic circuits which are formed with NOR-gates (or alternatively, NAND-gates) fed from replicate inputs, so that a comparatively high degree of reliability may be achieved by redundancies introduced in a compartively economical way. Each simple NOR function with k inputs is performed by r gates each having k times r inputs. Such systems of NOR gates tend to correct spurious zero signals, and the redundant components are arranged to make spurious one signals highly improbable. Corresponding systems of NAND-gates tend to correct spurious one signals and in these cases the redundancies must be arranged to make spurious zero signals improbable.
Another example of prior art techniques, is the use of parallel redundancy wherein mutually identical circuits or circuit elements are connected in paralled so that the operation is performed simultaneously by the parallel circuits or elements thereby producing identical outputs when all elements are functioning properly. If one circuit or element should cease to operate, the other or others will continue to operate and thus prevent interruption of the mission. However, these prior art techniques greatly increase the number of circuits in a system since one or more circuits are utilized to insure the operation of a particular function. The present invention utilizes an adaptive spare which may be utilized to provide any number of different functions thus reducing the spares requirement and increasing reliability.